In a traditional private network communication system, a scheduling station present only in a cluster communication system is responsible for functions of scheduling, grouping, calling, listening, etc. The scheduling station also bases its functioning upon a base station and transmits various signals to respective receiving devices through a radio frequency module of the base station with the use of a database inside the base station.
A mobile station remains passive of scheduling and functionality assigning processes, that is, the mobile station is under the control of both the scheduling station and a network management system. In a traditional application, the mobile station is only capable of performing functions of calling, transmitting information, etc. At present, there are generally two types of calls.
One of the two types is a uni-call. In this case, a mobile station calls another mobile station. The communication takes place between the two mobile stations (as illustrated in FIG. 1).
The other type is a group call. In this case, a single mobile station calls a fixed group of predetermined users (as illustrated in FIG. 2).
The group call here is predetermined. The group is specified in two approaches: one is to perform the setting of frequency modification (which refers to modification of a frequency corresponding to a channel for a mobile terminal) on a mobile station (e.g., a radiophone) to define a specific group which the radiophone can call and to define that the radiophone can responds to a call from a user in the group. The other application emerging recently is to perform dynamic grouping in a scheduling station or a network management terminal and to modify the internal setting of the radiophone via an air interface of a base station, which is similar to another frequency modification.
FIG. 3 illustrates a schematic diagram of a traditional scheduling station. As illustrated in FIG. 3, the traditional scheduling station bases its functioning upon a base station. Typically, the scheduling station software is installed in a Personal Computer (PC) which is connected with the base station via a serial interface or an IP network. The scheduling station software transmits a signal through a transmitting and receiving device of the base station to influence another mobile station or base station.
As can be apparent from FIG. 3, because the scheduling station software is installed in the PC, it may be inconvenient to displace the scheduling station which bases its functioning upon the presence of the base station. No scheduling function can be provided for a non-cluster communication system or for respective mobile stations in a direct communication mode.
In other words, it may be very inconvenient for a user to change temporarily the internal setting of a radiophone due to the necessary presence of devices including the scheduling station, a base station, etc.
For example, it is required to call temporarily mobile terminals A, B and D together so that a conference of a small section can be held as in an existing telephone conference function offered through telecommunication (this application approach is defined as a conference call mode). However, the conference call mode is currently available only to wired telephones but has not been involved in mobile communication. Therefore, it is necessary to apply the conference call mode to the mobile communication, particularly to the private network communication.
Moreover, current domestic digital private network systems generally adopting Time Division Multi Access (TDMA) can make efficient use of spectrum resources to thereby offer more extension possibilities for a single mobile terminal.
Traditional radiophones have very limited applications, and existing mobile stations generally still provide only simple communication and short message services. Although some advanced mobile stations can further provide other data services, it is still desired to further develop the extendibility of the mobile stations themselves, for example, to provide a user with specific service functions of a queue-on-busy call, an pre-emption call, identification of communication parties, dynamic regrouping, delayed joining, etc.
Moreover, it will be too late to set up a base station on the spot in an unexpected scenario. For example, a residence community occurring fire is originally provided with around 20 radiophones. In this case, it is not required to set up any base station and the radiophones works in a direction communication mode (i.e., the mobile stations communicates with each other directly without any network infrastructure). The firemen ask for some positional information, etc., presented from the security guards of the residence community, and the ambulance of 120 relieves injured residents. At this time, dealing with the fire will be facilitated significantly if the radiophones of the three sections can be arranged immediately in one group, which would otherwise be out of a support in the conventional art.
Dealing with some traffic accidents or the like may also present a temporary and exigent demand for concerted efforts of different sections, which nevertheless can not be accommodated in the conventional art.